In a sardonic response, he said: "You are of course, absolutely right. The time spent in my cafés will greatly help the profitability of our company.

"I'm sorry to have to pay you by cheque as I am aware of the effort and time it will take you to pay this into the bank."

EAT sent Mr McCrudden £15 worth of vouchers to spend in its shops. Matt Hart, the company's customer services manager, said: "Your idea of putting a value on the time our customers spend with us is new to us and is certainly a talking point now".

Little Chef sent Mr McCrudden £30 of vouchers "as a gesture of goodwill".

However, not all retailers have taken so well to the scheme. Nick Charlton, the managing director of Cranberry, the fruit and nut seller, initially retaliated with an invoice for £18.75 for the "12 minutes of my valuable time" that it took him to read Mr McCrudden's letter.

Mr McCrudden duly sent Mr Charlton a cheque – though included another invoice for time spent on a subsequent visit to Cranberry.